Binding of cellular proteins to a conformational domain of tumor suppressor protein p53.
Academic Article
Overview
Research
Identity
Additional Document Info
View All
Overview
abstract
The genes regulated by p53, as well as the factors modulating its function, need to be identified before the mechanism of action of p53 in control of cell growth can be adequately understood. Binding of the SV40 large T-antigen protein to an evolutionally conserved (conformational) domain of p53 inhibits p53's DNA-binding and transcription activation activities. Cellular proteins might also bind to this same region of p53 to regulate its function. A hybrid protein composed of protein A fused to the conformational domain (amino acids 115-295) of p53 was expressed in Escherichia coli and used as an affinity probe for binding proteins in detergent lysates of non-small cell lung carcinoma (NSCLC) cells. The wild-type p53 hybrid protein associated with several major proteins of molecular weights 45 K, 56 K, and 70 K, as well as other minor species ranging in molecular weight from 30 K to 90 K. These proteins bound specifically to the p53 sequence of the hybrid protein. Protein A did not associate with these proteins and the two p53 hybrid proteins containing missense mutations at codons 273 and 175 exhibited a 40-80% weaker association. In addition, T antigen competed with the cellular proteins for binding to the conformational domain. The conditions of cell growth had a profound effect on the expression of the p53 binding proteins. Considerably more p53 binding proteins were expressed in actively growing cells than in cultures maintained under conditions for slow growth. Quantitative differences in expression of p53-binding proteins were observed among different NSCLC cell lines. The expression of p53-binding proteins was not restricted to NSCLC cell lines; detergent extracts of an osteosarcoma cell line yielded similar p53-binding proteins.
